Wireless access systems have been widely deployed to provide various types of communication services such as voice or data. In general, a wireless access system is a multiple access system that supports communication of multiple users by sharing available system resources (a bandwidth, transmission power, etc.) among them. For example, multiple access systems include a Code Division Multiple Access (CDMA) system, a Frequency Division Multiple Access (FDMA) system, a Time Division Multiple Access (TDMA) system, an Orthogonal Frequency Division Multiple Access (OFDMA) system, and a Single Carrier Frequency Division Multiple Access (SC-FDMA) system.
The configurations of wireless access networks have recently been changed in such a manner that various types of small cells having small sizes (e.g., micro cells, pico cells, femto cells, etc.) interact with a macro cell having a relatively large size. This aims to increase Quality of Experience (QoE) by providing a high data rate to an end User Equipment (UE) in a situation where hierarchical multi-layer cells basically involving legacy macro cells co-exist.
According to Small Cell Enhancements for E-UTRA and E-UTRAN SI (refer to RP-122033), which is one of the current 3rd Generation Partnership Project (3GPP) standardization categories, discussion is under way to enhance indoor/outdoor scenarios using low power nodes, under the subject of small cell enhancement. Scenarios and requirements for small cell enhancement are disclosed in the 3GPP TR 36.932 standard.
Considering this trend, end UEs will be physically closer to a network in view of deployment of a large number of small cells within a macro cell. Therefore, it is expected that not legacy physical cell-based communication but UE-centered zone-based communication will be conducted in a future-generation wireless access network. To enable communication in a UE-centered zone for increasing capacity, technical issues should be induced and solved to realize a service providing unit such as a UE-centered zone differentiated from a legacy physical cell.
The emergence of small cells may significantly affect a current Remote Area Network (RAN). Particularly, the on/off characteristics of a small cell may affect deployment of a macro cell in terms of energy saving.